The present invention relates to the blades of rotary cutters. In particular, to blades which are required to be accurately located in a holder on a rotary drum.
Rotary cutters include one or more cutting blades which are removable from the body of the rotary cutter for replacement or adjustment. Blades need to be replaced when they become too dull or damaged. The blades may be released from the body of the rotary cutter by removing a blade holder assembly which fits in a pocket along the outer circumference of the cutter drum. The blade is then removed from the holder, sharpened or replaced, then reinstalled in the holder and the holder then reinstalled in the cutter drum.
Alignment problems often occur and the position of the blade with respect to the cutter drum is extremely critical to accurate cutting. The edge of the cutting blade needs to be exposed a very precise distance from the outside surface of the cutting drum. If the blade projects too far, the work is cut too deeply or blade damage may occur from excessive pressure. Conversely, if the blade does not project far enough, the material will not be sufficiently cut. In addition to the work being improperly or inaccurately cut, blade wear may become excessive. Not only does the blade need to project the correct amount, but its orientation needs to be set so that the cutting edge is precisely parallel to the axis of the rotating drum to ensure an even cut along its entire length. Thus, both of the demands of blade height and alignment are critical to the proper and efficient operation of a rotary cutter.
Prior art systems to set the proper height and alignment within the cutting blade holder comprise, for example, a simple hand-held, C-shaped gage as shown in FIG. 2. When using the gage, the blade is first loosened in the holder, and then the blade is advanced, holding the C-shaped gage between the base of the holder and the cutting edge. In order to assure that the cutting edge is parallel to the holder and therefore parallel to the cutting axis of the rotary drum, the gage is dragged across the length of the cutting edge to determine that the edge of the blade extends the proper height at all points. Cutting blades are extremely sharp and very sensitive, therefore the process of pulling the hand gage across the edge of the blade can damage or dull the blade. Furthermore, this process is extremely time-consuming since the cutting blade holder includes a multiplicity of adjusting screws and often setting the height of the blade at one point can change the height at another. Thus, the process is inefficient and time-consuming.
Another method for adjusting a cutting blade in a holder is disclosed in U.S. Pat. No. 3,600,816 issued to Watanabe. This patent discloses the use of a gage fixture into which the entire length of the cutting blade is placed so that it may be aligned along a single surface. The gage disclosed in this patent is used to adjust positioning members along the side surface of the blade, the blade is then transferred to the blade holder which has structures that interlock with the blade positioning members. One problem with this method, however, is that the junction between the blade positioning member and its interlocking element in the blade holder creates an additional tolerance which adds to the degree of possible misalignment between the cutting edge of the blade and the blade holder. Another problem is that the blade alignment elements of the gage are themselves adjustable screws. If the alignment screws are not adjusted properly, inaccuracy occurs. And finally, the Watanabe system requires a hand tool for setting the blade positioning means which abut alignment screws as they are set. The use of a separate hand tool introduces yet another possibility for operator error.
There is therefore a need in the art for a reliable, accurate and fast way to properly set the height of a cutting blade within its holder that simplifies the number of parts and provides a process which minimizes or eliminates operator error.
In order to meet the needs in the art described above, the present invention has been devised which utilizes a longitudinal gage fixture that extends the entire length of the cutting blade and which provides positively locked, parallel surfaces that uniformly and reliably set the proper height of the blade along its entire length while in the blade holder. This device requires no frictional movement of the gage along the length of the blade, and the setting of the blade may be achieved in an accurate, single step process. Most importantly, it adjusts the blade while it is in the blade holder without the need for removing the blade or intermediate adjusting elements.
According to the present invention, the entire blade and holder assembly is positioned within the gage fixture, therefore no intermediate positioning means between the blade and holder are needed. As further described herein the standard adjusting screws at the base of the holder are accessed through apertures in a baseplate of the gage fixture so that all necessary adjustments of the blade may be made with the holder insitu and without any movement of the holder. Only the movement of the blade within the holder is required during adjustment. Furthermore, once properly positioned, the tightening down of the blade may also be accomplished with the blade and holder still set within the gage fixture. Once the blade is properly set, the blade and holder, as the unit, may be removed from the fixture simply by retracting the spring-loaded top member, and then withdrawing the blade assembly out of the fixture.
More specifically, the Applicant has devised a blade height adjustment gage, comprising a gage fixture including a top member having an interior-facing blade contacting surface. Two, right and left side, spacer blocks and a baseplate are affixed to the fixture support plate. Each spacer block is of equal length so that when all parts are secured the base is parallel to the contact surface of the top member, the distance therebetween defining a predetermined gage height. Also, included are tool access means through the bottom of the baseplate whereby a tool may be inserted through the baseplate into the bottom portion of a blade holder. The blade holder is positioned within the fixture for moving the blade into contact with the contact surface area of the top member while the blade holder abuts an interior surface of the baseplate.
The method for blade adjustment according to the present invention comprises first removing the blade holder assembly from the cutter drum and loosening all the clamping and adjusting screws. The blade holder assembly is then placed into a gage fixture in which the top member is in its open position to receive the blade holder assembly. The top member is then moved to its closed position by screw drive means. The baseplate abuts the bottom surface of the blade holder and includes tool access means for inserting tool means through the baseplate to engage longitudinal adjusting screws on the blade holder which axially move the bottom of the blade at various points along its length. The blade is then moved by the adjusting screws until the cutting edge contacts an inside surface of a top member of the gage fixture. The blade holder clamp screws are then tightened. The gage fixture top member is then withdrawn and the blade holder assembly removed from the gage fixture. Finally, the blade holder is reinstalled into the cutter drum. This may be accomplished without any other structures frictionally moving across the cutting edge of the blade that might dull it.
These and other advantages of the present invention will be readily apparent to those of skill in the art from the following drawings and description of the preferred embodiment.